Active noise control system with horn sound feature

ABSTRACT

An active noise control system for use onboard a vehicle normally provides noise cancellation of engine sounds. The speaker of the active noise control system also emits a horn sound responsive to appropriate commands from a controller that receives a horn switch signal from a horn switch supported on a steering wheel assembly. The active noise control system controller enters a power saving mode when the vehicle ignition is turned off and the vehicle is not running. A horn switch activation during the power saving mode wakes up the controller so that the controller unmutes an amplifier and drives the speaker to emit the desired horn sound.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional ApplicationNo. 60/389,584, which was filed on Jun. 18, 2002.

BACKGROUND OF THE INVENTION

[0002] This invention generally relates to active noise control systemsfor vehicles. More particularly, this invention relates to operating anactive noise control system to provide a horn sound when a vehicle isnot running.

[0003] Most vehicles include a horn that is activated by pressing ormore switches typically mounted on a steering wheel assembly. The hornis properly used to notify other drivers or pedestrians of a vehicle'spresence or approach, for example. Typical horn assemblies include aphysical horn component mounted within the engine compartment that emitsthe horn sound responsive to appropriate switch activation.

[0004] Active noise control systems are well known. On modern vehicles,active noise control systems operate to cancel out noises associatedwith air intake assemblies, for example. A noise control systemtypically includes a speaker that is driven to emit a sound that cancelsout engine noise sounds that otherwise may be noticed by an individualwithin the passenger compartment. A controller drives the speaker toprovide the necessary noise cancellation signal or sound to provide thedesired effect.

[0005] With the advances available in electronics onboard vehicles,those skilled in the art are always striving to provide additionalfeatures and functions for the consumer. Further, there is always a needto strive for minimizing the expenses associated with supplying vehiclecomponents to manufacturers. This invention takes advantage of thecapabilities of an active noise control system and provides furthercapabilities that eliminates otherwise needed separate components suchas a horn.

SUMMARY OF THE INVENTION

[0006] In general terms, this invention is an active noise controlsystem that also provides a horn sound function even when the vehicle isnot running.

[0007] One example system designed according to this invention includesa speaker. A controller drives the speaker to produce a desired sound.The controller operates in a normal mode while the vehicle is runningand typically drives the speaker to produce a noise cancellation soundto cancel out noises associated with operation of the engine so thatsuch noises are not noticeable within the vehicle passenger compartment.The controller also operates in a power saving mode when the vehicle isnot running. The controller wakes up from the power saving moderesponsive to a horn switch activation that occurs when the vehicle isnot running. The controller then drives the speaker to emit a horn soundand returns to the power saving mode after the horn switch activation iscomplete.

[0008] In one example, the system includes an amplifier associated withthe speaker. The controller mutes the amplifier in the power saving modeand unmutes the amplifier responsive to the horn switch activation sothat the desired horn sound is produced.

[0009] The various features and advantages of this invention will becomeapparent to those skilled in the art from the following detaileddescription of a currently preferred embodiment. The drawings thataccompany the detailed description can be briefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 schematically illustrates an active noise control systemdesigned according to this invention supported on an example vehicle.

[0011]FIG. 2 is a flow chart diagram illustrating an example method ofcontroller operation designed according to this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0012]FIG. 1 schematically shows a vehicle 20 that includes an activenoise control system 22. A speaker 24 and an amplifier 26 are driven bya controller 28. The speaker 24 is associated with, for example, the airintake manifold of the vehicle to cancel out noises associated withengine operation that would otherwise be noticeable within the vehiclepassenger compartment. Known active noise cancellation techniquesprovide such results.

[0013] A steering wheel assembly 30 is supported within the vehiclepassenger compartment. A horn switch 32, which operates in aconventional manner, is supported on the steering wheel assembly 30. Inthe example arrangement, the horn switch 32 does not activate a separatehorn device supported within the engine compartment. Instead, the noisecontrol system 22 provides the horn sound using the speaker 24. Thecontroller 28 responds to activation of the horn switch 32 by drivingthe amplifier 26 and speaker 24 to emit a preselected horn sound.

[0014] The controller 28 operates in a normal operation mode while thevehicle is running. The controller 28 normally provides active noisecontrol in a conventional manner. In the event that the horn switch 32is activated, the controller 28 detects a horn switch activation andinterrupts the active noise control temporarily so that the speaker 24can be used to provide the desired horn sound.

[0015] It is desirable to provide an individual the ability to activatethe horn even when the vehicle is not running. The controller 28 entersa power saving, standby mode when the ignition is turned off and thevehicle is not running. The controller 28 interprets a horn switchactivation as a wake up signal when the controller is in the powersaving mode. The controller 28 then responds to the horn switchactivation by appropriately driving the speaker 24 to emit the hornsound.

[0016]FIG. 2 illustrates an example control strategy in flow chart form.At 42 the controller 28 is in the power saving mode. A horn switchactivation at 44 provides a wake up signal to the controller 28. In oneexample, the horn switch activation produces a low digital signal (i.e.,0) that is interpreted by the controller 28 as a wake up signal. Onceawakened, the controller 28 continues checking for a horn switchactivation signal every ten milliseconds at 46. The controller 28unmutes the amplifier 26 at 48 and drives the speaker 24 to emit thedesired horn sound at 50. In the illustrated example, the horn sound isgenerated for 200 milliseconds. The controller 28 continues checking forhorn switch activation and driving the speaker 24 to emit the horn soundas long as the signal is present.

[0017] Once the horn switch 32 is released, the determination at 46 isnegative. The controller 28 then mutes the amplifier at 52 and returnsto the power saving mode at 42.

[0018] In one example, the controller 28 comprises a digital signalprocessor (DSP). The DSP wakes up responsive to the horn switchactivation signal and then controls the amplifier 26 and speaker 24 asnecessary to achieve the desired horn sound. In another example, thecontroller 28 includes a microprocessor portion and a DSP portion. Inthis example, the microprocessor portion is responsible for handling thehorn activation when the controller is in the power saving mode. In thislatter example, the DSP remains in shutdown mode during horn activationwhen the vehicle is not running.

[0019] Those skilled in the art who have the benefit of this descriptionwill realize how best to select and arrange the electronics to achievethe horn activation strategy that best suits their particular needs.

[0020] The preceding description is exemplary rather than limiting innature. Variations and modifications to the disclosed examples maybecome apparent to those skilled in the art that do not necessarilydepart from the essence of this invention. The scope of legal protectiongiven to this invention can only be determined by studying the followingclaims.

I claim:
 1. An active noise control system for use on a vehicle,comprising: a speaker; and a controller that drives the speaker to emita desired sound, the controller operating in a normal mode when thevehicle is running, the controller operating in a power saving mode whenthe vehicle is not running, the controller wakes up responsive to a hornswitch activation and drives the speaker to emit a horn sound.
 2. Thesystem of claim 1, including an amplifier and wherein the controllermutes the amplifier in the power saving mode and then unmutes theamplifier responsive to a horn switch activation.
 3. The system of claim1, wherein the controller monitors whether a horn switch activationoccurs every ten milliseconds once the controller has woken up from thepower saving mode responsive to a horn switch activation.
 4. The systemof claim 3, wherein the controller drives the speaker to emit the hornsound for 200 milliseconds.
 5. The system of claim 1, wherein thecontroller comprises a digital signal processor and wherein the digitalsignal processor wakes up from the power saving mode and drives thespeaker responsive to the horn switch activation.
 6. The system of claim1, wherein the controller comprises a microprocessor and a digitalsignal processor and wherein the digital signal processor remains in apower saving mode during the horn sound production.
 7. The system ofclaim 1, wherein the controller responds to a horn switch activation inthe normal mode and drives the speaker to emit the horn sound.
 8. Amethod of producing a horn sound using a vehicle active noise controlsystem having a controller and a speaker, comprising the steps of:operating the controller in a normal mode while the vehicle is running;placing the controller in a power saving mode when the vehicle is notrunning; responding to a horn switch activation by waking up thecontroller from the power saving mode and driving the speaker to emit adesired horn sound responsive to the horn switch activation.
 9. Themethod of claim 1, wherein the active noise control system includes anamplifier associated with the speaker and including muting the amplifierwhen the controller is in the power saving mode and unmuting theamplifier responsive to the horn switch activation.
 10. The method ofclaim 8, including determining whether a horn switch activation occursevery ten milliseconds after waking up the controller from the powersaving mode.
 11. The method of claim 10, including returning thecontroller to the power saving mode when no horn switch activation ispresent for two consecutive checks.
 12. The method of claim 8, includingresponding to a horn switch activation when operating the controller innormal mode by driving the speaker to emit the desired horn sound. 13.The method of claim 12, including temporarily interrupting active noisecancellation responsive to the horn switch activation when operating thecontroller in normal mode.